Process of inhibiting corrosion

ABSTRACT

A process is disclosed for inhibiting corrosion in tin-plated steel aerosol cans which contain aqueous aerosol formulations and a propellant. Compositions such as the isopropylamine, cyclohexylamine, 2-ethylhexylamine and tertiary C 12-14  alkyl primary amine salts of N-acyl sarcosine; morpholine salts of oleic acid, acetic acid, benzoic acid, and N-acyl sarcosine; cyclohexylamine, 2-ethylhexylamine, tertiary C 12-14  alkyl primary amine and tertiary C 18-22  alkyl primary amine salts of benzoic acid are disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending application Ser. No. 07/174,497, now abandoned filed Mar. 25, 1988, which was a divisional of application Ser. No. 819,117, filed Jan. 15, 1986, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to corrosion inhibitor compositions and a process of inhibiting corrosion in aerosol products.

Many products designed for household, personal, automotive and other types of use are available as aerosol products. Examples of such aerosol products include: personal products such as hair care products (sprays, coloring agents and styling/conditioning mousses), deodorants, antiperspirants, first aid sprays, and colognes; household products such as waxes, polishes, pan sprays, insecticides and room fresheners; automotive products such as cleaners and polishes; industrial products such as cleaners, lubricants and mold release agents; and animal care products such as tick and flea repellants.

Although some aerosol products are packaged in glass bottles or aluminum cans or lined steel cans, most formulations are packaged in unlined cans made of tin-plated steel which may corrode during storage or use. While the tin affords some protection against corrosion, the thinness of the coating, imperfections in the surface, wear and tear, and chemical action may ultimately expose the steel to the contents of the can, and allow corrosion to occur. This corrosion can lead to contamination of the aerosol product and ultimately to the rupture of the can, if the corrosion is severe enough.

Water based aerosol formulations are being used increasingly to lower the flammability of the aerosol propellant and reduce manufacturing costs. However, the presence of water in an aerosol formulation increases the possibility of corrosion of tin-plated steel cans.

Usually a packaged aerosol contains both liquid and vapor phases and corrosion can occur on the interior surface of the can which is in contact with either phase. In addition, corrosion is more likely to occur when more than 80 ppm (parts per million) water is present. For example, in a system that includes dimethyl ether, a propellant and water, corrosion of the can which is in contact with the vapor phase may be aggravated by the fact that relatively large amounts of water vapor are present with the propellant; for example, the vapor phase of a 95/5 wt. % dimethyl ether/water system contains 7,750 ppm water vapor at 70° F. (21.1° C.). Moreover, the addition of ethanol to a DME/water system will often increase the amount of water vapor in the vapor phase and exacerbate the problem of vapor phase corrosion; a 90/5/5 (wt. %) DME/ethanol/water system will contain 9,100 ppm water vapor at 70° F.

Corrosion inhibitors are therefore useful when water-based aerosol formulations are packaged in tin-plated steel cans. However, many commercially available corrosion inhibitors are either ineffective for aerosol systems containing water or they fail to provide adequate protection against both liquid phase and vapor phase corrosion. It often happens that a corrosion inhibitor provides good liquid phase protection but fails to provide effective vapor phase protection. The reverse can also occur.

SUMMARY OF THE INVENTION

In accordance with this invention it has been found that corrosion of the interior of tin-plated steel containers which contain water-based aerosol formulations can be effectively controlled by the presence of an effective amount of a compound selected from the group consisting of C₃ to C₁₄ alkyl amine salts of N-acyl sarcosine, C₄ to C₂₂ alkyl amine salts of benzoic acid, C₄ to C₂₂ alkyl amine salts of oleic acid, salts of polyamines and oleic acid, and salts of imidazolines and oleic acid.

A process of inhibiting corrosion in a tin-plated steel aerosol can containing an aqueous aerosol formulation and a propellant comprising contacting the aqueous aerosol formulation, the propellant and an effective amount of a compound selected from the group consisting of C₄ to C₂₂ alkyl amine salts of oleic acid, and salts of polyamines and oleic acid, and salts of imidazolines and oleic acid with the interior of a tin-plated steel aerosol can.

DETAILED DESCRIPTION OF THE INVENTION

Certain amine salts have been found to be unexpectedly effective as corrosion inhibitors for tin-plated steel aerosol cans. The structures of these amine salts are:

(1) C₃ to C₁₄ alkyl amine salts of N-acyl sarcosine, where the acyl radical may be derived from coconut acids, lauric acid, oleic acid or mixtures thereof. The amines used may be isopropylamine, cyclohexylamine, morpholine, 2-ethylhexylamine and a tertiary alkyl primary amine such as Primene 81-R (branched C₁₂₋₁₄ alkyl primary amine sold by Rohm and Haas Company).

(2) C₄ to C₂₂ alkyl amine salts of benzoic or oleic acid where the amine used may be 2-ethylhexylamine, tertiary C₁₂₋₁₄ alkyl primary amine or tertiary C₁₈₋₂₂ alkyl primary amine. The amines used may also be cyclohexylamine and morpholine.

(3) Salts of polyamines such as N-tallow-1,3-diaminopropane and oleic acid.

(4) Salts of imidazolines such as 1-(2-hydroxyethyl) 2-tall oil-2-imidazoline and oleic acid.

By "tertiary alkyl" is meant that one carbon atom is bonded to three other carbon atoms.

By the term "coconut acids" is meant mixtures of C₈ to C₁₈ saturated fatty acids in which the C₁₂ acid fraction predominates. Also included are unsaturated acids such as oleic acid. The use of the term "coconut acids" is intended to include each component acid either alone or in mixture with other coconut acids which may occur in the technical or commercial grade of coconut acids. The individual acids may be derived from sources other than coconut oil, particularly when these individual acids are present in coconut oil in such small quantities that their isolation would be economically unattractive.

Even though tin-plated, steel aerosol cans may have steel surfaces which are subject to corrosive attack. The steel may be exposed because the tin plate is applied nonuniformly and/or may have porosity as applied. The seams which connect the sides, bottoms, and dome sections of the aerosol cans together often have unplated surfaces. In addition, the aerosol formulation may cause detinning of the tin-plate and thereby expose the underlying steel surface.

It is believed that the subject amine salts prevent corrosion of these exposed steel surfaces and/or detinning of the tin-plate itself by forming protective films in both the vapor and liquid phases. Certain of the subject amines, such as isopropylamine, cyclohexylamine and morpholine salts have unusual volatility and provide very good vapor phase corrosion protection as well as functioning as effective liquid phase rust inhibitors.

The subject amine salts can be used with a variety of propellants. Because they are essentially neutral compounds with respect to pH, they can be used with propellants such as FC-22 which is readily hydrolyzed at pH values above 8. In addition, the subject amine salts can be used with DME, which is particularly compatible with water. DME can be used either alone or in combination with other well known aerosol propellants such as: monochlorodifluoromethane (FC-22), 1-chloro-1,1-difluoroethane (FC-142b), 1,1-difluoroethane (FC-152a); hydrocarbons such as butane, isobutane and propane; compressed gases such as CO₂ and nitrogen; and mixtures of these propellants. The corrosion inhibitor compositions of this invention can be used in aerosols containing any of these propellants or combinations thereof.

The corrosion inhibitor compositions of this invention can usually be prepared by using commercially available materials. The corrosion inhibitor, the commercial designation and source for various of these compositions are shown later.

The effective concentration range of the subject corrosion inhibitor compositions is generally 0.1 to 1 wt. % based on the combined total weight of the propellant(s), the weight of the other ingredients and the corrosion inhibitor. A preferred weight range is 0.25 to 0.5 wt. % of the aerosol formulation.

The corrosion inhibitor compositions can be added to the aerosol system in different ways. They can either be added alone or mixed with other ingredients prior to introduction into the aerosol container. If preferred, they can also be combined with the propellant(s) first and subsequently this combination can be added to the aerosol container using well known techniques. This is a particularly convenient way to incorporate the inhibitor into the final aerosol formulation. For example, the subject amine salts are all soluble in DME and DME/FC-22 blends. Such solubility permits the DME or DME-blended propellant to be supplied to the aerosol formulator or loader with the corrosion inhibition composition already present. When combined with the propellant, the amount of corrosion inhibitor composition can be selected to provide the desired 0.1 to 1 wt. % of corrosion inhibitor composition in the final aerosol composition. U.S. Pat. No. 4,315,910 discloses methods for preparing and adding aerosol formulations and propellants to aerosol containers, which is hereby incorporated by reference.

The composition of the aqueous aerosol dispersible media which is, in essence, the formulation containing the active ingredients, will, quite naturally, depend upon the use for which the aerosol is designed. Such formulations are well known to persons skilled in the art, and the choice of formulation is not critical to the use of the invention so long as the medium is compatible with the components of the inhibitor composition. The use of the corrosion inhibitors in tin-plated cans with dry-type antiperspirants containing aluminum chlorohydrate is not recommended. Lined cans should be used in these instances.

It is common practice in the aerosol industry to evaluate corrosion inhibitors in accelerated aging tests. Thus, corrosion test data developed for aerosol cans of representative product formulations exposed to temperatures of 100°-120° F. have been found, through experience, to correlate well with the shelf-life of commercial products. Thus, 60-day tests at 120° F. which have been conducted for the subject corrosion inhibitors are expected to correlate well with actual product storage in stores, warehouses, etc.

EXAMPLES

Sixty-day corrosion tests at 120° F. (48.9° C.) were run on the corrosion inhibitors in four aerosol formulations. These formulations were selected as being representative of commercial products, in their chemical compositions. Distilled water was used in each of the formulations because it was readily available in the laboratory. However, similar results would be expected with deionized water which is often used in commercial aerosols.

Formulations

    ______________________________________                                         Components        Wt. %                                                        ______________________________________                                         #1 Insecticide (pH = 6)                                                        Pyrocide 175.sup.a                                                                               1.50                                                         Piperonyl butoxide                                                                               0.65                                                         "Witconol" 14.sup.b                                                                              0.97                                                         Ethanol (SDA-40-1)                                                                               10.01                                                        Water (distilled) 51.87                                                        Dimethyl ether    35.00                                                        ______________________________________                                          .sup.a Technical grade of natural pyrethrins (McLaughlin Gormley King          Company)?                                                                      .sup.b Polyglyceryl fatty acid ester surfactant (Witco Chemical Corp.).  

    #2 Insecticide (pH = 5)                                                        Dursban.sup.a     0.98                                                         Pyrocide 175      0.06                                                         Piperonyl butoxide                                                                               0.13                                                         MGK 264.sup.b     0.20                                                         Water (distilled) 63.63                                                        Dimethyl ether    35.00                                                        ______________________________________                                          .sup.a Phosphorothioic acid 0,0diethyl o(3,5,5-trichloro-2-pyridinyl)          ester (Dow Chemical Co.).                                                      .sup.b Insecticide synergist (McLaughlin Gormley King Company), Noctyl         bicycloheptane dicarboximide.                                            

    #3 Room Freshener (pH = 6)                                                     Fragrance.sup.a   1.40                                                         Ethanol (SDA-40-1)                                                                               19.60                                                        Water (distilled) 49.00                                                        Dimethyl ether    30.00                                                        ______________________________________                                          .sup.a Commercially available Rose Fragrance.                            

    #4 Insecticide (pH = 5)                                                        Dursban           0.98                                                         Pyrocide 175      0.06                                                         Piperonyl butoxide                                                                               0.13                                                         MGK 264           0.20                                                         Water distilled   63.63                                                        FC-22             14.00                                                        Dimethyl ether    21.00                                                        ______________________________________                                    

Procedure

All of the examples were prepared using the following procedure. The active ingredients were weighed individually into an eight-ounce three-piece aerosol can 21/8" in diameter and 5 9/16" long, except when the corrosion inhibitors were added to the aerosol can as a solution in the propellant (noted in tables). The can was purged with dichlorodifluoromethane (FC-12) vapor to displace the air in the container. The aerosol can valve was then placed into the can and crimped. The propellants were introduced into the can as liquids through the aerosol valve. Volume amounts corresponding to the weights of the propellants were calculated prior to loading, and a glass, calibrated, pressure buret was used to measure and transfer the liquids from storage cylinders to the can. A nitrogen gas pressure of 100 psig was applied to the buret to aid in transferring the liquids from the buret to the can. After the propellant was loaded, the can was weighed, and the weight of propellant recorded.

The aerosol cans used in the corrosion tests were commercially available containers and are described in trade literature as: one inch round dome top unlined aerosol containers, size 202×509 (21/8" diameter, 5 9/16" can wall height), 0.25 lb. electrolytic tin-plated (ETP), full concave bottom with welded side seam.

A corrosion test rating system was used which provides a complete visual description of the appearance of the interior surface of the tin-plated steel aerosol cans after 60 days storage at 120° F.

    ______________________________________                                         CAN CORROSION - RATING SYSTEM                                                  Rating*           Description                                                  ______________________________________                                         0                 No Corrosion                                                 1                 Trace Corrosion                                              2                 Light Corrosion                                              3                 Moderate Corrosion                                           4                 Heavy Corrosion                                              5                 Severe Corrosion                                             ______________________________________                                          *This numerical rating is an overall assessment of the total can               (tinplate, joints and side seams) and represents the primary rating of a       test. A rating of 0-2 is considered effective and 3 or greater is a faile      rating. Therefore, an effective amount of corrosion inhibiting compositio      in an aerosol formulation is the amount which is necessary to prevent mor      than light corrosion of the interior of a tinplated steel can which            contains an aqueousbased aerosol formulation, a propellant, and the            corrosion inhibiting composition.                                        

    ______________________________________                                         MATERIALS USED IN PREPARATION                                                  OF CORROSION INHIBITORS                                                        Material      Designation and Source                                           ______________________________________                                         Tertiary C.sub.12-14 alkyl                                                                   Primene 81-R (Rohm and Haas Co.)                                 primary amine                                                                  Tertiary C.sub.18-22 alkyl                                                                   Primene JM-T (Rohm and Haas Co.)                                 primary amine                                                                  N-oleyl sarcosine                                                                            Sarkosyl O (Ciba-Geigy Corp.)                                    N-lauroyl sarcosine                                                                          Sarkosyl L (Ciba-Geigy Corp.)                                    N-Cocoyl sarcosine                                                                           Sarkosyl LC (Ciba-Geigy Corp.)                                   Sodium N-oleyl                                                                               from Sarkosyl O (Ciba-Geigy                                      sarcosinate   Corp.)                                                           Sodium N-cocoyl                                                                              from Sarkoysl LC (Ciba-Geigy                                     sarcosinate   Corp.)                                                           Triethanolamine                                                                              Hamposyl TOC-30 (W. R. Grace                                     N-oleyl/cocoyl                                                                               & Co.)                                                           (70/30) sarcosinate                                                            2-Ethylhexylamine                                                                            Pfaltz and Bauer, Inc.                                           Morpholine    Pfaltz and Bauer, Inc.                                           Isopropylamine                                                                               Aldrich Chemical Company                                         Cyclohexylamine                                                                              Aldrich Chemical Company                                         Benzoic acid  Fisher Scientific Company                                        Oleic Acid    Fisher Scientific Company                                        N-tallow-1,3- Duomeen TDO (Armak Company)                                      diaminopropane                                                                 dioleate                                                                       1-(2-Hydroxyethyl)-                                                                          Witcamine PA-78B (Witco                                          2-tall oil-2- Chemical)                                                        imidazoline oleate                                                             ______________________________________                                    

                  TABLE I                                                          ______________________________________                                         CORROSION TEST DATA                                                            Corrosion Test Procedure - 60 days at 120° F.                           Corrosion Test Medium - Formulation #1                                                               Test    Description of                                   Corrosion Inhibitor                                                                          Wt. %   Rating  Test Can Corrosion                               ______________________________________                                         None          --      5       Bottom detinned; rust                                                          on walls; vapor phase                                                          corrosion                                        Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of Sarkosyl L                 corrosion                                        Primene 81-R salt                                                                            0.10    5       Similar to control                               of Sarkosyl LC                                                                 Primene 81-R salt                                                                            0.25    2       Light vapor phase                                of Sarkosyl LC                corrosion                                        Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of Sarkosyl LC                corrosion                                        Primene 81-R salt                                                                            0.10    5       Similar to control                               of Sarkosyl O                                                                  Primene 81-R salt                                                                            0.25    2       Light vapor phase                                of Sarkosyl O                 corrosion                                        Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of Sarkosyl O                 corrosion                                        Morpholine salt of                                                                           0.50    1       Slight liquid phase                              Sarkosyl O                    corrosion                                        Morpholine salt of                                                                           .sup. 0.50.sup.a                                                                       1       Slight liquid phase                              Sarkosyl O                    corrosion                                        Morpholine salt of                                                                           0.50    1       Slight corrosion in                              Sarkosyl O                    liquid                                           Cyclohexylamine salt                                                                         0.50    1       Slight corrosion in                              of benzoic acid               liquid                                           Witcamine PA-78 B                                                                            0.50    1       Slight corrosion in                                                            vapor                                            Duomeen TDO   0.50    2       Light corrosion                                                                in vapor                                         Primene 81-R salt                                                                            0.10    5       Similar to control                               of oleic acid                                                                  Primene 81-R salt                                                                            0.25    3       Moderate corrosion                               in of oleic acid              in vapor                                         Primene 81-R salt                                                                            0.50    2       Light corrosion in                               of oleic acid                 in vapor                                         Morpholine acetate                                                                           0.50    2       Light corrosion in                                                             liquid                                           Morpholine oleat                                                                             0.50    1       Slight corrosion in                                                            liquid                                           Cyclohexylamine                                                                              0.50    1       Slight corrosion in                              salt of oleic acid            liquid                                           Isopropylamine                                                                               0.50    1       Slight corrosion in                              salt of oleic acid            liquid                                           Isopropylamine salt                                                                          0.50    2       Light liquid phase                               of Sarkosyl O                 corrosion                                        2-Ethylhexylamine                                                                            0.10    3       Moderate vapor phase                             salt of Sarkosyl O            corrosion                                        2-Ethylhexylamine                                                                            0.25    2       Light vapor phase                                salt of Sarkosyl O            corrosion                                        2-Ethylhexylamine                                                                            0.50    2       Light vapor phase                                salt of Sarkosyl O            corrosion                                        Cyclohexylamine                                                                              0.50    1       Slight liquid phase                              salt of Sarkosyl O            corrosion                                        Primene 81-R salt                                                                            0.10    3       Moderate vapor phase                             of benzoic acid               corrosion                                        Primene 81-R salt                                                                            0.25    2       Light vapor phase                                of benzoic acid               corrosion                                        Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of benzoic acid               corrosion                                        Primene JM-T salt                                                                            0.50    2       Light vapor phase                                of benzoic acid               corrosion                                        2-Ethylhexylamine                                                                            0.10    3       Moderate vapor                                   salt of benzoic acid          phase corrosion                                  2-Ethylhexylamine                                                                            0.25    2       Light vapor phase                                salt of benzoic acid          corrosion                                        2-Ethylhexylamine                                                                            0.50    1       Slight vapor phase                               salt of benzoic acid          corrosion                                        ______________________________________                                          .sup.a Corrosion inhibitor added with propellant solution to aerosol can.

As can be seen from Table I, in each case the addition of an effective amount of corrosion inhibitor prevented more than light corrosion of the interior of the test can with Formulation No. 1. Specifically, more than 0.10 wt. % of Primene 81-R salt of Sarkosyl LC, Primene 81-R salt of Sarkosyl 0, Primene 81-R salt of oleic acid, 2-ethylhexylamine salt of Sarkosyl 0, Primene 81-R salt of benzoic acid, and 2-ethylhexylamine salt of benzoic acid was needed, but increased quantities provided effective corrosion inhibition.

                  TABLE II                                                         ______________________________________                                         CORROSION TEST DATA                                                            Corrosion Test Procedure - 60 days at 120° F.                           Corrosion Test Medium - Formulation #2                                                               Test    Description of                                   Corrosion Inhibitor                                                                          Wt. %   Rating  Test Can Corrosion                               ______________________________________                                         None          --      5       Severe corrosion in                                                            liquid and vapor                                                               phases                                           Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of Sarkosyl O                 corrosion                                        Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of benzoic acid               corrosion                                        Morpholine salt                                                                              0.50    1       Slight liquid phase                              of benzoic acid               corrosion                                        Morpholine salt                                                                              0.50    1       Slight liquid phase                              of oleic acid                 corrosion                                        Duomeen TDO   0.50    2       Light vapor phase                                                              corrosion                                        Duomeen TDO   .sup. 0.50.sup.a                                                                       2       Light vapor phase                                                              corrosion                                        ______________________________________                                          .sup.a Corrosion inhibitor added to aerosol can with propellant solution 

As can be seen from Table II, in each case the addition of 0.50 wt. % of corrosion inhibitor prevented more than light corrosion of the interior of the test can with Formulation #2.

                  TABLE III                                                        ______________________________________                                         CORROSION TEST DATA                                                            Corrosion Test Procedure - 60 days at 120° F.                           Corrosion Test Medium - Formulation #3                                                               Test    Description of                                   Corrosion Inhibitor                                                                          Wt. %   Rating  Test Can Corrosion                               ______________________________________                                         None          --      5       Bottom detinned;                                                               corrosion and detin-                                                           ning in vapor phase                              Primene 81-R salt                                                                            0.50    2       Light vapor phasee                               of Sarkosyl O                 corrosion                                        Primene 81-R salt                                                                            0.50    1       Slight vapor phase                               of benzoic acid               corrosion                                        Morpholine oleate                                                                            0.50    1       Slight liquid phase                                                            corrosion                                        Witcamine PA-78B                                                                             0.50    1       Slight vapor phase                                                             corrosion                                        Duomeen TDO   0.50    2       Slight vapor phase                                                             corrosion                                        ______________________________________                                    

As can be seen from Table III, in each case the addition of 0.50 wt. % of the corrosion inhibitor prevented more than light corrosion of the interior of the test can with Formulation No. 3.

                  TABLE IV                                                         ______________________________________                                         CORROSION TEST DATA                                                            Corrosion Test Procedure - 60 days at 120° F.                           Corrosion Test Medium - Formulation #4                                                               Test    Description of                                   Corrosion Inhibitor                                                                          Wt. %   Rating  Test Can Corrosion                               ______________________________________                                         None          --      5       Severe corrosion in                                                            liquid and vapor                                 Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of Sarkosyl O                 corrosion                                        Primene 81-R salt                                                                            0.50    2       Light vapor phase                                of benzoic acid               corrosion                                        Morpholine salt                                                                              0.50    0       No corrosion                                     of benzoic acid                                                                Morpholine salt                                                                              0.50    1       Slight corrosion in                              of oleic acid                 liquid                                           ______________________________________                                    

As can be seen from Table IV, in each case the addition of 0.50 wt. % of corrosion inhibitor prevented more than light corrosion of the interior of the test can with Formulation No. 4. 

I claim:
 1. A process of inhibiting corrosion in a tin-plated steel aerosol can containing an aqueous aerosol formulation and a propellant comprising contacting the aqueous aerosol formulation, the propellant and an effective amount of a compound selected from the group consisting of C₄ to C₂₂ alkyl amine salts of oleic acid, and salts of polyamines and oleic acid, and salts of imidazolines and oleic acid with the interior of a tin-plated steel aerosol can.
 2. The process of claim 1 wherein the compound is present in an amount between 0.1 to 1.0 wt. % based on the total weight of the aqueous aerosol formulation and the propellant.
 3. The process of claim 2 wherein the compound is present in an amount between 0.25 to 0.5 wt. % based on the total weight of the aqueous aerosol formulation and the propellant.
 4. The process of claim 1 wherein the polyamine is N-tallow-1,3-diaminopropane.
 5. The process of claim 4 wherein the compound is present in an amount between 0.1 to 1.0 wt. % based on the total weight of the aqueous aerosol formulation and the propellant.
 6. The process of claim 5 wherein the compound is present in an amount between 0.25 to 0.5 wt. % based on the total weight of the aqueous aerosol formulation and the propellant.
 7. The process of claim 1 wherein the imidazoline is 1-(2-hydroxyethyl)2-tall oil-2-imidazoline.
 8. The process of claim 7 wherein the compound is present in an amount between 0.1 to 1.0 wt. % based on the total weight of the aqueous aerosol formulation and the propellant.
 9. The process of claim 8 wherein the compound is present in an amount between 0.25 to 0.5 wt. % based on the total weight of the aqueous aerosol formulation and the propellant. 